Glass substrates and semiconductor wafers are cleaned by a cleaning apparatus in manufacturing processes for, for example, liquid crystal displays and semiconductor devices. These substrates are cleaned in accordance with a technique such as brush cleaning using a cleaning liquid or ultrasonic cleaning, and after that, rinsed with pure water or the like (cleaning step), and then, the pure water for rinsing is removed from the front and rear surface of the substrate (drying step). In recent years, in the drying step, an air knife has been widely used. The air knife is usually formed in such a manner that steam or a gas is jetted in band form from a slit.
FIG. 13 is a plan diagram showing the apparatus for processing a substrate 900 of Patent Document 1.
In FIG. 13, a substrate 90 in a state of being wet with a processing liquid is discharged from a portion for processing a substrate 901, for example, a cleaning apparatus or a polishing processing apparatus, and is mounted on a roller conveyor 902 of apparatus for processing a substrate 900. The rollers of roller conveyor 902 rotate, and thereby, substrate 90 is conveyed in the direction of the arrow in the figure. A pair of air knives 903 for removing the liquid from the front and rear surfaces of substrate 90 so as to dry the substrate are provided above and below the substrate on the path of conveyance of substrate 90.
Air knives 903 are respectively installed in such a manner as to be inclined by approximately 30° relative to the direction perpendicular to the direction in which substrate 90 is conveyed by roller conveyor 902 in the plane where substrate are conveyed, have an opening in slit form for gas discharge which covers the area between the two ends of the substrate in the direction perpendicular to the direction in which substrate 90 is conveyed, and blows air in band form on substrate 90 which passes directly beneath or directly above the air knife, at a point that is at an appropriate distance from portion for processing a substrate 901.
In FIG. 13, when substrate 90 passes by air knives 903, the liquid on the front and rear surface of substrate 90 is swept to the downstream side in the direction in which substrate 90 is conveyed, and after that, the liquid on the front and rear surfaces of substrate 90 is swept so as to move from corner B to corner A on the downstream side in the direction in which substrate 90 is conveyed.
FIG. 14 is a cross sectional diagram showing the air knives for drying the front and rear surface of a substrate 90 which are disclosed in Patent Document 2. An upper air knife 910 which is placed on the upper surface of substrate 90 is provided with a gas jetting portion 911 for jetting, for example, compressed air, and a mist collecting portion 912, and a lower air knife 920 which is placed on the lower surface of substrate 90 is provided with a gas jetting portion 921 and a mist collecting portion 922 in the same manner as upper air knife 910.
A liquid adheres to the upper surface of substrate 90 in the state of a liquid film La, and a liquid adheres to the lower surface of substrate 90 in the state of innumerable liquid drops Lb. When substrate 90 is conveyed in the direction of the arrow in the figure so as to pass by air knife 910 and air knife 920, gas jetting portions 911 and 921 of the respective air knives 910 and 920 blow a gas, for example, compressed air, on the front and rear surface of substrate 90, respectively, in the diagonally downward and diagonally upward direction from jetting openings 913 and 923.
All of liquid film La on the upper surface of substrate 90 is blown on the side opposite to the direction in which substrate 90 is conveyed, and at the same time, mist is created above substrate 90, and this mist is sucked by mist collecting portion 912.
In addition, liquid drops Lb on the lower surface of substrate 90 are converted to mist, in the same manner as on the upper surface of substrate 90, and are sucked by mist collecting portion 922.
Patent Document 1: Japanese Unexamined Patent Publication 2001-284310
Patent Document 2: Japanese Unexamined Patent Publication 2003-229404